Plants including at least two free piston auto-generators intended to work in given phase relation to each other



g- 1966 A. MOIROUX ETAL 3,2 7, 16

PLANTS INCLUDING AT LEAST TWO FREE PISTON AUTO-GENERATORS INTENDED TOWORK IN GIVEN PHASE RELATION TO EACH OTHER Filed July 7, 1964 as 2Z1J03] 2325 l]- 5 I'1 55 e. 39 q E9 1 I I I 20 20%) 30 J; 12 c 15 v 6 i f615 6a 16 152; 6a

6 6 5 66 5 v I a m -6 4 E z iii 1 Q I H 3 3 .9"3 9 J 3 J0 p \I 4 4 I 2CF I i 5 I 7 7 1 l E l I I 1 INVENTOR 4 9b 7E flId/Izu K J24 7 5 ,W "'52ATTORNEKS 7 United States Patent 3,267,916 PLANTS INCLUDING AT LEAST TWOFREE PISTON AUTO-GENERATORS INTENDED TO WORK IN GIVEN PHASE RELATION TOEACH OTHER Auguste Moiroux and Jean Guy, Lyon, France, assignors toSociete dEtudes et de Participations, Eau, Gaz, Electricite, EnergieS.A., Geneva, Switzerland Filed July 7, 1964, Ser. No. 380,832 Claimspriority, application France, July 25, 1963, 942,694 6 Claims. (Cl.12346) The present invention relates to a plant including at least twofree piston auto-generators intended to work in predetermined phaserelation respectively. The invention is more especially concerned Withthe case of two auto-generators having communicating casings, or even asingle casing common to both of them, said two autogenerators working inphase opposition (that is to say with a phase difference of 180) saidauto-generators being hereinafter called twin auto-generators.

Free piston auto-generators generally comprise a device, calledstabiliser, which controls the amount of air present in their returnenergy accumulators (cushions) in such manner as to ensure a stableoperation. Such a stabiliser is generally cont-rolled, on the one hand,by a factor which is a function of the load of the auto-generator, thisfactor 'being, as a rule, the pressure existing in the air reservoir(casing) of the auto-generator, and, on the other hand, by a pressurecorresponding to a value which is characteristic of the mass of air inthe cushion. This characteristic value is, for instance, either the meanof the instantaneous pressuresexisting in the cushion during anoscillation of the free piston of the auto-generator, or the pressureexisting in the.cushion for a given position of the free piston therein.

It is also known to keep the operation of the free pistons of severalauto-generators either in phase or with a given phase offsetting byvarying, by means of a device called dephaser, the ratio of therespective masses of air present in the cushions of said auto-generatorsso as to adjust said masses when there is a perturbation in the phaserelation between the auto-generators. This adjustment, corresponding toa variation of the ratio of the air masses in the respective cushions,may be obtained by transferring a portion of the air present in thecushion of the auto-generator which is leading into the cushion of theauto-generator which is lagging until the desired phase relation hasbeen restored.

In the known plants of the kind in question which include a dephaser,each stabiliser is controlled by pressures which are characteristic onlyfor the cushion or cushions of the auto-generator to which thestabiliser belongs. It will be understood that the action of thedephaser may then have a disturbing effect upon the respectivestabilisers of the auto-generators. On the other hand, these stabilisersmay interfere with the action of the dephaser.

The object of the present invention is to obviate these drawbacks.

To this effect, in a plant including at least two free pistonauto-generators and a dephaser for maintaining the desired phaserelation between them, the stabilisers of the respective auto-generatorsare controlled, on the one hand, by a factor which is a function of theload of the plant, and, on the other hand, by a factor which correspondsto the mean value of the characteristic pressures in the cushions of theauto-generators.

This permits of obtaining an adjustment of all the air masses containedin the cushions of the auto-generators instead of an individual andindependent adjustment of the respective cushions of theauto-generators. This excludes any disturbance, whether it is producedby the operation of the stabilisers during the dephasing action or bythe dephasing during the operation of the stabilisers.

A preferred embodiment of the present invention will be hereinafterdescribed with reference to the appended drawing, given merely by way ofexample, and in which:

FIG. 1 diagrammatically shows a plant including twin free pistonauto-generators mounted in phase opposition, and a dephaser, this plantbeing made according to the present invention;

FIG. 2 diagrammatically shows a modification.

The plant shown by FIG. 1 comprises two free piston auto-generators Aand B intended to work in phase opposition. Each of theseauto-generators comprises a motor cylinder 1 provided with inlet ports 2and exhaust ports 3, these ports being controlled by motor pistons 4moving in opposed directions, respectively, in motor cylinder 1. Each ofsaid motor pistons 4 is rigid with a compressor piston 5 slidable in acompressor cylinder 6.

Compressor piston 5 divides the corresponding cylinders into twochambers 6a and 6b. Chamber 6a, located on the external side of piston5, constitutes :a return energy pneumatic accumulator, or cushion.Chamber 6b, located on the inner side of piston 5, constitutes thecompressor cham'ber proper and is provided with intake valves 7 anddelivery valves 8. These last mentioned valves control the passage ofcompressed air from compressor chamber 6b into casing 9, which surroundsmotor cylinder 1 and which constitutes a reservoir for air serving tofeed and to scavenge said motor cylinder 1. The inlet ports 2 of motorcylinder 1 communicate with said casing 9.

The two movable sets of free pistons 4 and 5 of every auto-generator areinterconnected by a synchronizing device, not shown by the drawing, madein any known manner, for instance consisting of a lever oscillatingabout a fixed axis and connected through rods with the two sets ofpistons.

In order to have in the two cushions of a given autogenerator equalinstantaneous pressures these two cushions are connected together by aconduit, not shown.

Each motor cylinder 1 is fitted with a fuel introduction device, forinstance an injector, not shown, fed by means of an injection pump.

The two casings 9 of the juxtaposed auto-generators A and B communicatetogether through a conduit 10.

The exhaust openings of motor cylinders -1 are conneoted with a commonexhaust pipe '11 which leads the power gases issuing through exhaustports 3 to a receiver machine to be driven by said gases, for instance aturbine. If the two auto-generators are in opposed phase relation, thepressure variations in exhaust pipe 11 are small.

The means serving to produce and to maintain a phase relation betweenbetween auto-generators A and B are adapted, if the actual phaserelation difiers from the desired relation, to cause air to flow fromthe cushions of the auto-generator that is leading to the cushions ofthe auto-generator that is laggin thus slowing down one of theseauto-generators and accelerating the other until the desired phaserelation is restored. Such a dephaser may include, as described in theFrench Patent No. 999,940, filed February 5, 1946 by Raul Pa-terasPescara and the firm called Societe dEtudes et de Participations, Eau,Gaz, Electricit, Energie, SA.

Such a dephaser includes a floating piston 12 pro vided with a flange,so that said piston has, in a stepped cylinder where it moves, foursurfaces a, b, c, d. Surfaces a .and b are subjected to the action ofthe instantaneous pressures in cushions 6a, these pressures beingtransmitted to said surfaces through conduits 13 of relatively largecross section. Surfaces c and d are subjected to the action of pressuresequal to the mean value of the instantaneous pressures existing in saidcushions 6a. For this Patented August 23, 1966 purpose, the spaces towhich said surfiaces c .and d belong are connected with cushions 6athrough channels 14 of small cross section. Finally, piston 12 issubjected to the actions of two opposed springs 15 and 16 which urge thefloating piston into its mean position. This floating piston 12 isconnected to a slide valve 17 interposed in a conduit 18 interposedbetween the respective cushions 6a of auto-generators A and B so as toconnect said cushions together when the aperture 17a of said slide valveis in line with conduit 18.

The operation of this dephaser is as follows:

As long as the free pistons of the twin auto-generators maintain thedesire-d phase opposition (180), the amplitude of the oscillations ofthe system constituted by ports 12 and '17 is not sufficient to causeconduit 18 to be opened by slide value 17. On the contrary, if the phaseopposition is no longer maintained, the amplitude of the oscillations ofthe oscillating system increases and slide valve 17 opens conduit 18 attimes such that the cushion of the leading auto-generator is partlydischarged into the cushion of the lagging auto-generator until thedesired 180 phase relation is restored.

In order to adapt the mass of air in cushions 6a to the load of thecorresponding auto-generator, each generator comprises a stabiliserwhich increases the mass of air in the cushions thereof when the load ofthe corresponding auto-generator increases and which drives out air fromsaid cushions when the load of the auto-generator decreases.

The respective stabilisers of the auto-generators are controlled by acommon element which is subjected, on the one hand, to the action of thepressures existing in the common casing of the two auto-generators, and,on the other hand, to the action of a pressure corresponding to the meanvalue of the characteristic pressures in the cushions of theauto-generators.

-In the plant of FIG. 1 the characteristic pressure of the cushions isequal to the mean of their instantaneous pressures.

This characteristic pressure is obtained in a space 19 which isconnected through conduits 20 to the respective cushions 6a of theauto-generators. Each of these conduits 20 is provided, for instance atthe place Where it opens into space 19, with a throttled portion 20a.Thus space 19 receives the mean pressures in cushions 6a. Furthermorespace .19 is connected through a conduit 21 provided with a throttledportion 21a to one of the ends of a cylinder .22 in which is slidablymounted a piston 23. The other end of said cylinder 22 is connectedthrough a conduit 24 with the common casing 9 of the twinauto-generators. Therefore piston 23 is subjected on one side to theaction of a pressure which is the mean value of the mean pressuresexisting in the cushions 6a of the twin auto-generators, and on theother side, to the action of the pressure existing in casing 9. Piston23 constitutes the common control member for both of the stabilisers ofthe respective auto-generators.

In the embodiment of FIG. 1, these two stab-ilisers comprise ,a singlehollow slide .valve 25 and a single cylinder 26 in which said slidevalve 25 is movable. This slide valve is divided into two compartmentsby a partition 27, one of these compartments belonging to the stabiliserof one of the auto-generators and the other to the stabiliser of theother auto genera-tor. Each of these compartments is divided by a wall27 into two chambers one of which is provided with a check valve 28opening toward the inside of the slide valve, whereas the other chamberis provided with a check valve 29 opening from the corresponding chamberinto cylinder 26. This cylinder 26 communicate-s, through a conduit 30with the in side of casing 9 and it is provided in its side wall withtwo ports 31, 32, one of which, 3d, is connected through a conduit 33with the air cushion 6a of auto-generator B, whereas the other port, 32,is connected. through conduit 34, to the cushion 6a of the otherauto-generator A.

Each compartment of slide valve 25 is provided with two openings, 35,36. If the pressure rises in casing 9 so that piston 23 and slide valve25 rigid therewith are moved toward the right from their neutralposition (in which ports 31 and 32 are closed by the slide valve) ports35 are placed in communication with ports 31 and 32 provided in the sidewall of cylinder 26. In this case, air may flow from casing 9, throughcheck valves 28, into cushions 6a to increase the mass of air presenttherein. On the contrary, if the pressure in casing 9 decreases, piston23 and slide valve 25 rigid therewith are moved toward the left, whichplaces the ports 36 of the slide valve opposite the ports 31, 32provided in the side Wall of cylindrical housing 26. In this case aportion of the air present in cushions 6a may escape through checkvalves 29 into cylindrical housing 26 and thence into casing 9.

Advantageously, slide walve 25 is subjected to the action of anadjustable spring 3-7 interposed between a disc 38 rigid with controlpiston 23 and a fixed abutment 39 the position of which may be adjustedby means of a threaded rod 40. This threaded rod may be controlledeither manually or automatically.

In view of the fact that slide valve 25, common to both of thestabilisers, is controlled by the mean of the characteristic pressure ofcushions 6a, this slide valve, in case of variation of the load, variesthe whole of the air masses which are located in the cushions of the twoauto-generators without the operation of the two stabilisers beinginfiuenced by the distribution of the total air mass between thecushions of the two auto-generators, which takes place in particularduring the periods for which the dephaser works to restore the desireddephasing. The operation of this dephaser is therefore not disturbed bythe operation of the stabilisers. On the other hand the effect of thedephaser has no disturbing influence upon the operation of thestabilisers.

In some cases it may be advantageous to separate the two stabiliserswhile having them controlled, as above stated, by a common member. Thisseparation permits of varying their relative position so as tocompensate, if need be, for the internal disymmetries which may existbetween two twin auto-generators. This modification is illustrated byFIG. 2.

According to this embodiment, piston 23 controls two slide valves 25aand 2515 connected together through a threaded rod 41 rigid with slidevalve 25a and a nut 42 rigid with slide valve 25b. These two slidevalves are movable in a common cylindrical housing 26a provided withports 31a and 32a communicating with the respective cushions 6a of thetwo auto-generators. In order to vary the distance between slide valves25a and 25b to compensate for disymmetries between the auto-generators,it sufiices to rotate one of the slide valves, for instance 25!), withrespect to the other slide valve. This rotation is effected by means ofcontrol wheel 46. Each of the slide valves 25 and 25b is provided, inits end wall, with two sets of check valves 28a, 29a and 28b, 2%. Eachhollow slide valve is divided by a partition 27a, 27b into twocompartments. One of the sets of check valves perunits air to flow fromcylinder 26a into one of the compartments of the corresponding slidevalve and the other set of check valves permits air to flow out from theother compartment of the slide valve into cylinder 26a. Finally each ofthe slide valves is provided, in its side walls, with ports 35a, 36a,and 35b, 36b located on opposite sides of the partition which dividesthe inside of the hollow slide valve into two compartments.

The operation of the stabiliser of FIG. 2 is analogous to that of thestabiliser illustrated by FIG. 1.

According to a modification, the two stabilisers, instead of beingcontrolled by a single part, are each provided with its own controlpart, the respective control parts being placed, on the one hand, underthe action of the pressure in the casing, and, on the other hand, underthe action of a pressure corresponding to the mean value of thecharacteristic pressures in the cushions of the autogenerators.According to another modification the control part or parts of thestabilisers is, or are, actuated not by said pressures but by forces(either electrical or hydraulic) variable in accordance with saidpressures.

In a general manner, while we have in the above description disclosedwhat we deem to be a practical and etficient embodiment of ourinvention, it should be well understood that we do not wish to belimited thereto as there might be changes made in the arrangement,disposition and form of the parts without departing from the principleof the present invention as comprehended within the scope of theappended claims.

What we claim is:

1. A plant which comprises, in combination, at least two free pistonauto-generators, each of said auto-generators comprising a motor unitand a compressor unit, said motor unit including two motor elements, amotor piston and a motor cylinder, one movable in the other to formbetween them a variable volume fuel combustion chamber, said compressorunit including two compressor elements, a compressor piston and acompressor cylinder, one movable in the other, each of said compressorelements being fixed to one of said motor elements, respectively, acasing fixed with respect to said motor cylinder for feeding compressedair thereto, said compressor elements forming between them on the onehand an air compression chamber for feeding said casing with compressedair and on the other hand a closed air cushion chamber the volume ofwhich is reduced on every increase of volume of said fuel combustionchamber, whereby expansion of said air cushion produces every returnstroke of said motor piston, a conduit having one end thereof incommunication with said air cushion chamber, and a stabiliser mounted tocontrol the communication between the other end of said conduit and saidcasing, said stabiliser including a cylindrical housing, a hollow slidevalve slidable in said casing and having a neutral position therein andcheck valve means carried by said slide valve arranged to open throughsaid slide valve a unidirectional communication from said casing to saidconduit when said slide valve is moved from said neutral positionthereof in one direction and a unidirectional communication from saidconduit to said casing when said slide valve is moved from said neutralposition thereof in the other direction, means for producing apredetermined phase relation between the respective operations of saidauto-generators, and means for urging the slide valve of each of saidstabilisers in said first direction in response to an increase of theload of the plant and, in said second direction in response to anincrease of the mean value of respective pressures characteristic of thepressures in the cushion chambers of said auto-generators, respectively.

2. A plant which comprises, in combination, at least two free pistonauto-generators, each of said auto-generators comprising a motor unitand a compress-or unit, said motor unit including two motor elements, amotor piston and a motor cylinder, one movable in the other to formbetween them a variable volume fuel combustion chamber, said compressorunit including two compressor elements, a compressor piston and acompressor cylinder, one movable in the other, each of said compressorele ments being fixed to one of said motor elements, respectively, acasing fixed with respect to said motor cylinder for feeding compressedair thereto, said compressor elements forming between them on the onehand an air compression chamber for feeding said casing with com pressedair and on the other hand a closed air cushion chamber the volume ofwhich is reduced on every increase of volume of said fuel combustionchamber, where by expansion of said air cushion produces every returnstroke of said motor piston, a conduit having one end thereof incommunication with said air cushion chamber, and a stabiliser mounted tocontrol the communication between the other end of said conduit and saidcasing, said stabiliser including a cylindrical housing, a hollow slidevalve slidable in said casing and having a neutral position therein andcheck valve means carried by said slide valve arranged to open throughsaid slide valve a unidirectional communication from said casing to saidconduit when said slide valve is moved from said neutral positionthereof in one direction and a unidirectional communication from saidconduit to said casing when said slide valve is moved from said neutralposition thereof in the other direction, means for producing apredetermined phase relation between the respective operations of saidauto-generators, and means for urging the slide valves of saidstabilisers in said first direction in response to an increase of thepressure in said casings, and in said second direction in response to anincrease of the mean values of the instantaneous pressures existing inthe cushion chambers of said auto-generators, respectively.

3. A plant which comprises, in combination, at least two free pistonauto-generators, each of said auto-generators comprising a motor unitand a compressor unit, said motor unit including two motor elements, amotor piston and a motor cylinder, one movable in the other to formbetween them a variable volume fuel combustion chamber, said compressorunit including two compressor elements, a compressor piston and acompressor cylinder, one movable in the other, each of said compressorelements being fixed to one of said motor elements, respectively, acasing fixed with respect to said motor cylinder for feeding compressedair thereto, said compressor elements forming between them on the onehand an air compression chamber for feeding said casing with compressedair and on the other hand a closed air cushion chamber the volume ofwhich is reduced on every in crease of volume of said fuel combustionchamber, whereby expansion of said air cushion produces every returnstroke of said motor piston, a conduit having one end thereof incommunication with said air cushion chamber, and a stabiliser mounted tocontrol the communication between the other end of said conduit and saidcasing, said stabiliser including a cylindrical housing, a hollow slidevalve slidable in said casing and having a neutral position therein andcheck valve means carried by said slide valve arranged to open throughsaid slide valve a unidirectional communication from said casing to saidconduit when said slide valve is moved from said neutral positionthereof to one direction and a unidirectional communication from saidconduit to said casing when said slide valve is moved from said neutralposition thereof in the other direction, means for producing apredetermined phase relation between the respective operations of saidauto-generators, and a single member for urging the slide valves of bothof said stabilisers in said first direction in response to an increaseof the load of said plant, and in said second direction in response toan increase of the mean value of respective pressures characteristic ofthe pressures in the cushion chambers of said auto-generators,respectively.

4. A plant according to claim 3 wherein said stabilisers comprise acommon cylinder and, fitting slidably in said last mentioned cylinder, ahollow slide valve operatively connected with said member, alongitudinal partition for dividing said slide valve into twocompartments, a wall for dividing each of said compartments into twoportions, check valves carried by one end wall of said slide valveopening toward the inside of one of said compartment, portions checkvalve means carried by the other wall of said slide valve opening towardthe outside of the other of said compartment portions.

5. A plant according to claim 3 wherein said stabilisers comprise acommon cylinder and, fitting slidably in said last mentioned cylinder,two coaxial hollow slide valves belonging respectively to saidstabilisers, further comprising means for adjusting the positions ofsaid slide valves with respect to each other.

6. A plant according to claim 3 wherein said stabilisers comprise acommon cylinder and, fitting slidably in said last mentioned cylinder,two coaxial hollow slide valves belonging respectively to saidstabilisers, further comprising nut and screw means for adjusting thepositions of said slide valves with respect to each other.

No references cited.

5 MARK NEWMAN, Primary Examiner. W. E. BURNS, Assistant Examiner.

1. A PLANT WHICH COMPRISES, IN COMBINATION, AT LEAST TWO FREE PISTON AUTO-GENERATORS, EACH OF SAID AUTO-GENERATORS COMPRISING A MOTOR UNIT AND A COMPRESSOR UNIT, SAID MOTOR UNIT INCLUDING TWO MOTOR ELEMENTS, A MOTOR PISTON AND A MOTOR CYLINDER, ONE MOVABLE IN THE OTHER TO FORM BETWEEN THEM A VARIABLE VOLUME FUEL COMBUSTION CHAMBER, SAID COMPRESSOR UNIT INCLUDING TWO COMPRESSOR ELEMENTS, A COMPRESSOR PISTON AND A COMPRESSOR CYLINDER, ONE MOVABLE IN THE OTHER, EACH OF SAID COMPRESSOR ELEMENTS BEING FIXED TO ONE OF SAID MOTOR ELEMENTS RESPECTIVELY, A CASING FIXED WITH RESPECT TO SAID MOTOR CYLINDER FOR FEEDING COMPRESSED AIR THERETO, SAID COMPRESSOR ELEMENTS FORMING BETWEEN THEM ON THE ONE HAND AN AIR COMPRESSION CHAMBER FOR FEEDING SAID CASING WITH COMPRESSED AIR AND ON THE OTHER HAND CLOSED AIR CUSHION CHAMBER THE VOLUME OF WHICH IS REDUCED ON EVERY INCREASE OF VOLUME OF SAID FUEL COMBUSTION CHAMBER, WHEREBY EXPANSION OF SAID AIR CUSHION PRODUCES EVERY RETRUN INCREASE OF SAID MOTOR PISTON, A CONDUIT HAVING ONE END THEREOF IN COMMUNICATION WITH SAID AIR CUSHION CHAMBER, AND A STABILISER MOUNTED TO CONTROL THE COMMUNICATION BETWEEN THE OTHER END OF SAID CONDUIT AND SAID CASING, SAID STABILISER INCLUDING A CYLINDRICAL HOUSING, A HOLLOW SLIDE VALVE SLIDABLE IN SAID CASING AND HAVING A NEUTRAL POSITION THEREIN AND CHECK VALVE MEANS CARRIED BY SAID SLIDE VALVE ARRANGED TO OPEN THROUGH SAID SLIDE VALVE A UNIDIRECTIONAL COMMUNICATION FROM SAID CASING TO SAID CONDUIT WHEN SAID SLIDE VALVE IS MOVED FROM SAID NEUTRAL POSITION THEREOF IN ONE DIRECTION AND A UNIDIRECTIONALCOMMUNICATION FROM SAID CONDUIT TO SAID CASING WHEN SAID SLIDE VALVE IS MOVED FROM SAID NEUTRAL POSITION THEREOF IN THE OTHER DIRECTION, MEANS FOR PRODUCING A PREDETERMINED PHASE RELATION BETWEEN THE RESPECTIVE OPERATIONS OF SAID AUTO-GENERATORS, AND MEANS FOR URGING THE SLIDE VALVE OF EACH OF SAID STABILISERS IN SAID FIRST DIRECTION IN RESPONSE TO AN INCREASE OF THE LOAD OF THE PLANT AND, IN SAID SECOND DIRECTION IN RESPONSE TO AN INCREASE OF THE MEAN VALUE OF RESPECTIVE PRESSURES CHARACTERISTIC OF THE PRESSURES IN THE CUSHION CHAMBERS OF SAID AUTO-GENERATORS, RESPECTIVELY. 